The polyurethane resin, the reaction product of 1,4-polybutadiene polyol and isocyanate, is excellent in rubber elasticity.The features of polyurethane resin are its low glass transition temperature and good rubber elasticity property even at low temperature.Moreover, it is excellent in water resistance because of the hydrophobic polybutadiene in its molecular frame.In addition, the insulation property of it is as good as epoxy resin and silicone resin. However, 1,4-polybutadiene polyol is in the form of liquid with high viscosity so that it is unsuitable for potting.Therefore, by the means of mixing ricinoleic polyol of a low viscosity, the workablitiy of 1,4~polybutadiene(Polybutadiene)polyol will be substantially improved without deteriorating other properties.
As one approach of advanced packaging technologies, high reliability Liquid Mold UnderFill (Liquid MUF) materials and unique process will be presented here. Liquid MUF materials have the features of high adhesion, low CTE and low modulus. It is possible to alleviate the stress of the solder of each device mounted in the package, and they have excellent reliability too. These materials are adjusted the workability depending on the application. Moreover, because of low viscosity, the Liquid MUF material could be mold-underfilled with relatively lower stress to large Flip Chip devices with small gap and narrow pitch compared to the conventional solid materials. As for the processes of the liquid materials, printing, dispensing and compression molding are applicable. In this paper, the printing process, especially vacuum printing encapsulation systems (VPES) and pressure curing systems, will be mainly discussed. In addition, module package structure that achieved by these material and process development will be also explained in detail.
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